According to new data analysis from CoreLogic, a large earthquake along the San Andreas fault impacting both Northern and Southern California simultaneously – once considered impossible – could cause up to 126 percent more residential property damage than previously thought, putting more homes at risk and increasing loss estimates in a state already at high risk for earthquake damage. The CoreLogic analysis is based on revised earthquake risk science from the Uniform California Earthquake Rupture Forecast, Version 3 (UCERF3), which has concluded that a single large earthquake could now rupture simultaneously in both Northern and Southern California, and that earthquakes of magnitude 8.0 and higher will affect a larger land area and greater number of people. In particular, the San Andreas fault has always been viewed as two independent segments with earthquake ruptures on the northern and southern San Andreas faults deemed mutually exclusive of one another.
Based on the revised UCERF3 hazard data, CoreLogic has produced new earthquake risk analysis that illustrates the higher conditional probability of losses for an earthquake impacting both regions simultaneously. Figures 1-4 show four earthquake scenarios in California and the resulting increase in both the number of single-family homes that could be damaged and the accompanying reconstruction cost value (RCV).
The CoreLogic analysis shows that an earthquake of magnitude 8.3 along the San Andreas fault, that previously was thought to only occur along the northern segment of the fault line, could result in a full rupture and increase the number of homes damaged by 126 percent, from 1.6 to 3.5 million homes, and increase RCV by 79 percent, from $161 billion to $289 billion. A similar scenario that expands earthquake risk from just the southern San Andreas fault to a full rupture increases the number of homes damaged by 54 percent, from 2.3 million to 3.5 million, and increases RCV by 111 percent, from $137 billion to $289 billion. For a magnitude 8.2 or 8.0 earthquake scenario, the rupture, while smaller, would still impact both regions of the fault and much of the geography of the state, as well as increase the number of homes damaged and the RCV (Figures 3 and 4). The estimated number of homes damaged includes those that sustain damage of 5 percent or more of the total reconstruction cost value the property.
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